This invention relates to electrically conductive diacetylene polymers. More particularly, it is concerned with structurally modified polydiacetylenes.
The general chemical structure for polydiacetylenes is ##STR1## where R and R' are suitably chosen side groups which will vary from polymer to polymer. The fully conjugated backbone of the polydiacetylene provides a one-dimensional electronic structure, well insulated from other chains by the bulky side groups, R and R'.
Polydiacetylenes are formed through a topochemical solid state polymerization when diacetylene monomers are subjected to thermal or a variety of radiative excitations. The resulting polydiacetylene is in the form of a macroscopic "perfect" single crystal often with dimensions greater than one millimeter on all sides. The polydiacetylene crystals are highly anisotropic and can be made essentially defect free. The polymer may also be obtained in the form of a monolayer or multilayer film.
Fully crystalline polydiacetylenes have been reported to exhibit carrier mobilities comparable to silicon or gallium arsenide. For example, the diacetylene polymer from the bis(p-toluene-sulfonate) of 2,4-hexadiyne-1,6-diol (PTS) has been reported to exhibit exceptionally high carrier mobilities along its chain direction, .mu..about.20 m.sup.2 S.sup.-1 V.sup.-1. The long carrier mean free paths implied clearly follow from the full order of these polymers. Polydiacetylenes may have application in all optical signal processing due to the very high values of their third-order nonlinear susceptibilities X.sup.3 (.omega.).
A major limitation in employing polydiacetylenes as an electronic material is the relative inability to systematically create major changes in the electrical and optical properties of these materials. Previously reported attempts to chemically create changes in the electrical and optical properties of PTS and other polydiacetylenes by halogen oxidation have been generally unsuccessful.
Although very high carrier mobilities have been reported for polydiacetylenes, their applications as electronic materials have been limited by the inability to chemically or otherwise modify the electronic properties, such as electrical conductivity, prior to the present invention.